Electronic devices, such as e-book readers and smartphones are constrained by the capacity of their batteries, requiring recharge after some period of usage. Increasing the capacity of these batteries to extend battery life increases the mass of the device, which in many circumstances is undesirable.
To recharge the device's battery without connecting to the power grid, solutions exist where the device is connected to an external battery pack, such as device “case” that includes a secondary battery, or battery pack that connects to the device by a Universal Serial Bus (USB) connector. However, these cases and other external battery packs can be improved. Described herein are technical solutions to improve the use of these and other types of devices.